1. Field of the Invention
The present invention relates to a toroidal coil layer having, particularly, lower layer coil pieces and upper layer coil pieces, and formed to be wound around a magnetic layer as an axis, and more specifically, to a magnetic head and a manufacturing method thereof capable of forming upper layer coil pieces to be formed on an insulating layer having a step in a predetermined shape with high precision, reducing the yoke length, and improving the recording efficiency.
2. Description of the Related Art
The structure of a toroidal coil layer, which is formed to be wound around the magnetic layer using one magnetic layer serving as an axis, is disclosed in JP-A-5-242429, JP-A-5-250636 and JP-A-5-342529(hereinafter, referred as to “cited references”).
As disclosed in the cited references, the toroidal coil layer is configured to have lower layer coil pieces formed below a magnetic layer serving as an axis and upper layer coil pieces above the magnetic layer. Also, ends of the lower layer coil pieces and ends of the upper layer coil pieces are provided to face each other in a thin film thickness, and these ends are electrically connected to each other, thereby forming a toroidal coil layer.
For example, FIG. 15 shows a conventional shape of the lower layer coil pieces, and FIG. 16 shows a conventional shape of the upper layer coil pieces. Both of FIGS. 15 and 16 are partial plan views of the upper layer coil pieces and the lower layer coil pieces.
As shown in FIG. 15, a plurality of lower layer coil pieces 1 are arrayed in a height direction (Y-direction) from the facing surface to a recording medium (a direction opposite to the Y-direction in the drawing). Each lower layer coil piece 1 is formed in a shape symmetrical with respect to a centerline A drawn in the height direction from almost the center in a track width direction (X-direction in the drawing). As shown in FIG. 15, each lower coil piece 1 is composed of a straight region 1a extending in a direction parallel to the track width direction (X-direction in the drawing) and curved regions 1b curved in the height direction (Y-direction) from both ends of the straight region 1a, and ends 1c of the curved regions 1b of each lower layer coil piece 1 become connecting spots with the upper layer coil pieces 2.
As shown in FIG. 16, a plurality of upper layer coil pieces 2 are arrayed in a height direction (Y-direction) from the facing surface to a recoding medium (a direction opposite to the Y-direction in the drawing). Each upper coil piece 2 is composed of a straight region 2a extending in a direction substantially parallel to the track width direction (X-direction in the drawing) and a curved region 2b curved in the height direction (Y-direction) from a lower end (in the drawing) of the straight region 2a, and both ends 2c of each upper layer coil pieces 2 become connecting spots with the lower layer coil pieces 1.
As shown in the cited references, each upper layer coil piece 2 is formed from a swelled coil insulating layer 3 covering a magnetic layer as an axis to an insulating layer 4 which is widened on both sides of the coil insulating layer 3 and is one-step lower than the coil insulating layer 3.
An end of a lower layer coil piece 1 shown in FIG. 15 and denoted by the character “B” is electrically connected to an end 2c of an upper layer coil piece 2 denoted by the character “B”, an end 1c of a lower layer coil piece 1 denoted by the character “C” is electrically connected to an end 2c of the upper layer coil piece 2 denoted by the character “C”, an end 1c of the lower layer coil piece 1 denoted by the character “D” is electrically connected to an end 2c of an upper layer coil piece 2 denoted by the character “D”, and an end 1c of the lower layer coil piece 1 denoted by the character “E” is electrically connected to an end 2c of the upper layer coil piece 2 denoted by the character “E”. If ends 1c and 2c of the other lower and upper layer coil pieces 1 and 2 are electrically connected to each other in this way, a toroidal coil layer is completed.
Otherwise, as shown in the cited references (for example, refer to FIG. 2 of JP-A-5-242429 and FIG. 2 of JP-A-5-342529), all the upper layer coil pieces 2 are formed in a shape extending in the direction parallel to the track width direction (X-direction in the drawing), while the lower layer coil pieces 1 are formed in a shape inclined in the height direction (Y-direction in the drawing) with respect to the track width direction). Also, the ends 2c of the upper layer coil pieces 2 and the ends 1c of the lower layer coil pieces 1 are electrically connected to each other, respectively, thereby completing a toroidal coil layer.
However, the toroidal coil layer composed of the lower layer coil pieces 1 and the upper layer coil pieces 2 shown in FIGS. 15 and 16, and a toroidal coil layer composed of lower layer coil pieces 1 and upper layer coil pieces 2 shown in FIG. 17 have the following problems, respectively.
The toroidal coil layer composed of the lower layer coil pieces 1 and the upper layer coil pieces 2 shown in FIGS. 15 and 16, has a problem in that the upper layer coil pieces 2 cannot be formed in a predetermined shape with high precision.
FIG. 17 is a manufacturing process view showing a process of manufacturing the upper layer coil pieces 2, and a partial sectional view of a magnetic head during the manufacturing process when the magnetic head is cut along a line I-I (the line I-I runs along an end of the coil insulating layer 3 in the track width direction) shown in FIG. 16 and is viewed from the direction of arrows.
As shown in FIG. 17, a resist layer 5 is coated from the top of the insulating layer 4 to the top of the coil insulating layer 3, and a punched pattern 5a having the same shape as the upper layer coil pieces 2 is formed in the resist layer 5 by exposure development.
Meanwhile, as described above, the coil insulating layer 3 has a shape that is swelled upwardly from the surface of the insulating layer 4. For this reason, as shown in FIG. 18, a step P is formed between both side ends 3a of the coil insulating layer 3 in the track width direction (X-direction in the drawing) and the surface of the insulating layer 4. In addition, FIG. 18 is a partial sectional view of a magnetic head during the manufacturing process when the magnetic head is cut along a line II-II shown in FIG. 16 and is viewed from the direction of arrows.
Each upper layer coil piece 2, as described referring to FIG. 16, is composed of a straight region 2a and a curved region 2b, and a portion of the curved region 2b is formed to be just caught by the step P. Also, since the curved regions 2b are disposed obliquely with respect to the direction (Y-direction in the drawing) that the end 3a of the coil insulating layer 3 extends, the punched pattern of the curved regions 2b cannot be formed with high precision due to irregular reflection as shown in FIG. 18, which may be caused in the step P in exposure development when the punched pattern of the curved regions 2b is formed.
As specific problems, adjacent upper layer coil pieces 2 are electrically connected to each other in the curved regions 2b, or defective portions such as holes are formed in the curved regions 2b. 
Meanwhile, in the case of the toroidal coil layer shown in FIG. 19, particularly, the lower layer coil pieces 1 are obliquely arranged in the height direction (Y-direction in the drawing) from a direction parallel to the track width direction (X-direction in the drawing). Therefore, a formation region of the lower layer coil pieces 1 is widened in the height direction (Y-direction in the drawing). As a result, a problem occurs in that the yoke length of a magnetic layer may easily increase. Also, there is a problem that the recording efficiency may deteriorate due to an increase in inductance caused by an increase in the yoke length.